Sintered hard metal alloy



Aug.l 18, 1959 J o.`w. oHLssoN 2,899,739

SINTERED HARD METAL ALLOY Filed June 11, 1957 INVE/VTR Fall, Johan @lofW/Uiam @l1/ssen BJ JOMJW 89 ffornejs 2,899,739 Patented Aug. v18, 19592,899,739 Y SINTERED HARD METAL ALLOY' Fall Johanl lof William Ohlsson,Enskede, Sweden, as-

sgnor to Sandvikens Jernverks Aktiebolag, Sandviken, Sweden, acorporation of Sweden Application June '11, '1957, Serial No. 664,943

6 Claims. (Cl. 29182.7)

The present invention'relates to a sintered hard metal alloy'of the wellknown type consisting essentially of tungsten carbide and titaniumcarbide (with or without a content of tantalum and/or niobium carbide)and an auxiliary or bonding metal selected preferably from the irongroup of the periodic table, for'instance cobalt, nickel and/or iron,and which has a structure built up of the following phases:

ly-Phase consisting of a solid solution of WC and TaC/NbC (if present)in TiC, ,t9-phase consisting of auxiliaryV or bonding metal (hereinaftercalled bonding metal), usually Co and/ or Ni, and a-phase consisting ofWC.

For machine tool cutters for the finishing of steel, hardl metal alloyshave been used consisting of -7% yby weight Co and a high TiC content,for example 20-36% by weight. been included in the alloy. As an exampleof known alloys'for this purpose I mention below the vapproximateproportions of two main types:

A, percent by weight B, percent by weight 6 balance The alloys of thetype A have relatively satisfactory strength qualities, while their wearresistance is considerably .lower than that obtainable by the alloysofthe type B, the latter, however, having the drawback of being veryfragile.'

'I'he object of the present invention is to produce a sintered hardmetal alloy which has the qualities both of satisfactory strength and ofsatisfactory wear resistance. Alloys according to the present inventionhave been found to be particularly suitable for machine tools forfinishing materials like steel giving long chips, but are not limited tothis particular application. Y

A sintered hard metal alloy according to the present invention isdefined both by the percentages of its components present in the alloy,and by a relationship between the amounts of the and y-phases in thealloy.

Takingy first the components of the alloy, a sintered hard metal alloyaccording to the present invention contains 30-45% by weight TiC, 1-5%by weight TaC/NbC and 8-l3% by weight of bonding metal such as Co, Ni

and/or Fe, the remainder being substantially all WC, although, as knownin this art, other alloy components,

' for example, one or more of the carbides of molybdenum,

chromium, vanadium and zirconium may be present in small amounts withoutdisadvantage to the essential propv erties of the alloy. Furthermore, ofcourse, whether or not these alloy components are present, the alloy ofthe invention is likely to contain certain impurities; thus, forexample, the components TaC/N bC used for hard metal In some cases asmall amount of TaC hasl 2 alloys always ncontain. smalll(insignificant) amounts ofV oxygen and nitrogen, and WC sometimesmayhcontain small (insignificant) amounts of molybdenum carbide.

A sintered hard metal alloy according to` the present inventionis alsocharacterized in that the amount of the ,I3-phase of the alloy and theamount ofthe ^yphase arel related to one another by` the relationship`10o 1oo-2 wherein and fy represent the amounts of the respective phasesexpressed in volume percent. Preferably.

ly 100 1.5 Any tendency to deformation of the cutting edge which mayoccur with high bonding metal contents when .usinghigh cutting speedwhich give rise to high temperatures,

' that the alloy contains either or both the compounds TaC and NbC, andthat where a percentage ligure is given against the expression TaC/NbCthis refers'to the con# tent of (TaC-l-NbC) in the alloy.

The bonding metal usually consists substantiallyY en tirely of Co and/or Ni. I have found that with the relatively high proportion of TiCincluded in the alloy of the present invention it may be advantageous touse Ni as a bonding metal, as Ni has a greater capacity for dissolvingTiC than has Co.

In comparison with knownA hard metal alloys for finish`V ing materialssuch as steel the alloy of thisinvention has an increased amount -phaseAof the alloy whilst maintaining or even increasing the resistance towear, that is to say resistance against wear as well as cratering. Inpreviously known hard 'metals for the purpose specified, the amount ofy-phase has been less than 1GO-2;?, whilst the amount of bonding metalhas been considerably below the limits specifiedfor Vthis invention.

For obtaining the unusual properties for lthe hard metal alloy accordingto this invention the composition off-'the alloyis of great importance.-The limits ofV the values of the components havebeen --indicated above.Ithas usually proved .to be advantageous if the hard metal contains upto 5% by weight (preferably between 1 and 3% by weight) of TaC/NbC. Theamount of the bonding metal is preferably chosen within the range 8-ll%by i TiC percent 36442 TaC/NbC do 1-3 Bonding metal, preferably Coand/or Ni do I 9-11 WC Y remainder The invention will now be illustratedby some examples giving the approximate composition by weight forcertain alloys in accordance with the invention.

Example I Percent by weight TiC i. 40 TaC/NbC 2 Co l0 WC 48 This has'been shown to` be of importance for obtaining an increase in thestrength 3 t Exampie 2 1 1 1 proportions offthesecomponents :aregroilndzwth .tungf steni carbide and :bonding metal tov af grainsizewhichwil give: 'the -islinfteredi hardg metal falloy fproductf af grain;sjiz fof preferabiyiz; ma: After prrssnsepottims mthiww der, to alsuitable szeandf shape they are suitably sintere i in ava'cuunz 'ovematlaboutll for; about 1; hour.; i i f me Qi ffplass; ab .by

The alloy con if; @ai

,v i 11's* n; by weight fof fther iltiardfrnetals; wa

:De per= cbm andi they snm nii lthe' anhzmnts= of the three phasesa, f f

, f 'andere equals lfwhere j,;;ar1d=fyfrepressre1th www@ of therespective ypliasesin volumes percent.- f f f f f g2; A isintered;hartigmetalf Lalioy accordinglzto; claim :I wherein? tire amount by:-weighti 'ci fthe TEGy content y l accordance Wit invention it has beenproved to be advantageous to add titanium carbide in the form of aso-called double car# bide (Ti, W) C, consisting of for example 50% byWeight of titanium carbide and 50% by weight of tungsten carbide.Tantalum carbide and/or niobium carbide may either be added in the formof single carbides or in the form of a solid solution (Ta, Nb)C. Ofcourse, it is References Cited m the me of thls patent also possible toinclude carbides in other solid solutions, Schwarzkopf: PowderMetallurgy, Its Physics and Profor example in the form of (T, Ta, W)C.The correct duction, Macmillan Co., New York (1947), pp. 208-211.

1.A SINTERED HARD METAL ALLOY CONSISTING ESSENTIALLY OF THE FOLLOWINGCOMPONENTS IN THE FOLLOWING PERCENTAGES BY WEIGTH: TIC, 30 TO 45%; ACARBIDE OF THE GROUP CONSISTING OF TAC AND NBC, 1 TO 3%; AUXILIARYBONDING METAL OF THE GROUP CONSISTING OF NI, CO AND FE, 8-11%; THEREMAINDER BEING SUBSTANTIALLY ALL WC, SAID ALLOY BEING FURTHERCHARACTERIZED IN THAT SAID ALLOY IS COMPOSED OF A Y-PHASE CONSISTING OFA SOLID SOLUTION, IN TIC, OF ALL OF THE CARBIDE OF THE GROUP CON SISTINGOF TAC AND NBC AND SUBSTANTIALLY ALL OF WC AND AN A B-PHASE CONSISTINGTHE REMAINING UNDISSOLVED WC AND B-PHASE CONSISTING OF AUXILIARY BONDINGMETAL THE AMOUNT OF THE B-PHASE THEREOF AND THE AMOUNT OF THE Y-PHASETHEREOF BEING RELATED TO ONE ANOTHER BY THE RELATIONSHIP